Java example source code file (Temporal.java)
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* Copyright (c) 2012, Stephen Colebourne & Michael Nascimento Santos
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package java.time.temporal;
import java.time.DateTimeException;
/**
* Framework-level interface defining read-write access to a temporal object,
* such as a date, time, offset or some combination of these.
* <p>
* This is the base interface type for date, time and offset objects that
* are complete enough to be manipulated using plus and minus.
* It is implemented by those classes that can provide and manipulate information
* as {@linkplain TemporalField fields} or {@linkplain TemporalQuery queries}.
* See {@link TemporalAccessor} for the read-only version of this interface.
* <p>
* Most date and time information can be represented as a number.
* These are modeled using {@code TemporalField} with the number held using
* a {@code long} to handle large values. Year, month and day-of-month are
* simple examples of fields, but they also include instant and offsets.
* See {@link ChronoField} for the standard set of fields.
* <p>
* Two pieces of date/time information cannot be represented by numbers,
* the {@linkplain java.time.chrono.Chronology chronology} and the
* {@linkplain java.time.ZoneId time-zone}.
* These can be accessed via {@link #query(TemporalQuery) queries} using
* the static methods defined on {@link TemporalQuery}.
* <p>
* This interface is a framework-level interface that should not be widely
* used in application code. Instead, applications should create and pass
* around instances of concrete types, such as {@code LocalDate}.
* There are many reasons for this, part of which is that implementations
* of this interface may be in calendar systems other than ISO.
* See {@link java.time.chrono.ChronoLocalDate} for a fuller discussion of the issues.
*
* <h3>When to implement
* <p>
* A class should implement this interface if it meets three criteria:
* <ul>
* <li>it provides access to date/time/offset information, as per {@code TemporalAccessor}
* <li>the set of fields are contiguous from the largest to the smallest
* <li>the set of fields are complete, such that no other field is needed to define the
* valid range of values for the fields that are represented
* </ul>
* <p>
* Four examples make this clear:
* <ul>
* <li>{@code LocalDate} implements this interface as it represents a set of fields
* that are contiguous from days to forever and require no external information to determine
* the validity of each date. It is therefore able to implement plus/minus correctly.
* <li>{@code LocalTime} implements this interface as it represents a set of fields
* that are contiguous from nanos to within days and require no external information to determine
* validity. It is able to implement plus/minus correctly, by wrapping around the day.
* <li>{@code MonthDay}, the combination of month-of-year and day-of-month, does not implement
* this interface. While the combination is contiguous, from days to months within years,
* the combination does not have sufficient information to define the valid range of values
* for day-of-month. As such, it is unable to implement plus/minus correctly.
* <li>The combination day-of-week and day-of-month ("Friday the 13th") should not implement
* this interface. It does not represent a contiguous set of fields, as days to weeks overlaps
* days to months.
* </ul>
*
* @implSpec
* This interface places no restrictions on the mutability of implementations,
* however immutability is strongly recommended.
* All implementations must be {@link Comparable}.
*
* @since 1.8
*/
public interface Temporal extends TemporalAccessor {
/**
* Checks if the specified unit is supported.
* <p>
* This checks if the specified unit can be added to, or subtracted from, this date-time.
* If false, then calling the {@link #plus(long, TemporalUnit)} and
* {@link #minus(long, TemporalUnit) minus} methods will throw an exception.
*
* @implSpec
* Implementations must check and handle all units defined in {@link ChronoUnit}.
* If the unit is supported, then true must be returned, otherwise false must be returned.
* <p>
* If the field is not a {@code ChronoUnit}, then the result of this method
* is obtained by invoking {@code TemporalUnit.isSupportedBy(Temporal)}
* passing {@code this} as the argument.
* <p>
* Implementations must ensure that no observable state is altered when this
* read-only method is invoked.
*
* @param unit the unit to check, null returns false
* @return true if the unit can be added/subtracted, false if not
*/
boolean isSupported(TemporalUnit unit);
/**
* Returns an adjusted object of the same type as this object with the adjustment made.
* <p>
* This adjusts this date-time according to the rules of the specified adjuster.
* A simple adjuster might simply set the one of the fields, such as the year field.
* A more complex adjuster might set the date to the last day of the month.
* A selection of common adjustments is provided in {@link TemporalAdjuster}.
* These include finding the "last day of the month" and "next Wednesday".
* The adjuster is responsible for handling special cases, such as the varying
* lengths of month and leap years.
* <p>
* Some example code indicating how and why this method is used:
* <pre>
* date = date.with(Month.JULY); // most key classes implement TemporalAdjuster
* date = date.with(lastDayOfMonth()); // static import from Adjusters
* date = date.with(next(WEDNESDAY)); // static import from Adjusters and DayOfWeek
* </pre>
*
* @implSpec
* <p>
* Implementations must not alter either this object or the specified temporal object.
* Instead, an adjusted copy of the original must be returned.
* This provides equivalent, safe behavior for immutable and mutable implementations.
* <p>
* The default implementation must behave equivalent to this code:
* <pre>
* return adjuster.adjustInto(this);
* </pre>
*
* @param adjuster the adjuster to use, not null
* @return an object of the same type with the specified adjustment made, not null
* @throws DateTimeException if unable to make the adjustment
* @throws ArithmeticException if numeric overflow occurs
*/
default Temporal with(TemporalAdjuster adjuster) {
return adjuster.adjustInto(this);
}
/**
* Returns an object of the same type as this object with the specified field altered.
* <p>
* This returns a new object based on this one with the value for the specified field changed.
* For example, on a {@code LocalDate}, this could be used to set the year, month or day-of-month.
* The returned object will have the same observable type as this object.
* <p>
* In some cases, changing a field is not fully defined. For example, if the target object is
* a date representing the 31st January, then changing the month to February would be unclear.
* In cases like this, the field is responsible for resolving the result. Typically it will choose
* the previous valid date, which would be the last valid day of February in this example.
*
* @implSpec
* Implementations must check and handle all fields defined in {@link ChronoField}.
* If the field is supported, then the adjustment must be performed.
* If unsupported, then an {@code UnsupportedTemporalTypeException} must be thrown.
* <p>
* If the field is not a {@code ChronoField}, then the result of this method
* is obtained by invoking {@code TemporalField.adjustInto(Temporal, long)}
* passing {@code this} as the first argument.
* <p>
* Implementations must not alter this object.
* Instead, an adjusted copy of the original must be returned.
* This provides equivalent, safe behavior for immutable and mutable implementations.
*
* @param field the field to set in the result, not null
* @param newValue the new value of the field in the result
* @return an object of the same type with the specified field set, not null
* @throws DateTimeException if the field cannot be set
* @throws UnsupportedTemporalTypeException if the field is not supported
* @throws ArithmeticException if numeric overflow occurs
*/
Temporal with(TemporalField field, long newValue);
//-----------------------------------------------------------------------
/**
* Returns an object of the same type as this object with an amount added.
* <p>
* This adjusts this temporal, adding according to the rules of the specified amount.
* The amount is typically a {@link java.time.Period} but may be any other type implementing
* the {@link TemporalAmount} interface, such as {@link java.time.Duration}.
* <p>
* Some example code indicating how and why this method is used:
* <pre>
* date = date.plus(period); // add a Period instance
* date = date.plus(duration); // add a Duration instance
* date = date.plus(workingDays(6)); // example user-written workingDays method
* </pre>
* <p>
* Note that calling {@code plus} followed by {@code minus} is not guaranteed to
* return the same date-time.
*
* @implSpec
* <p>
* Implementations must not alter either this object or the specified temporal object.
* Instead, an adjusted copy of the original must be returned.
* This provides equivalent, safe behavior for immutable and mutable implementations.
* <p>
* The default implementation must behave equivalent to this code:
* <pre>
* return amount.addTo(this);
* </pre>
*
* @param amount the amount to add, not null
* @return an object of the same type with the specified adjustment made, not null
* @throws DateTimeException if the addition cannot be made
* @throws ArithmeticException if numeric overflow occurs
*/
default Temporal plus(TemporalAmount amount) {
return amount.addTo(this);
}
/**
* Returns an object of the same type as this object with the specified period added.
* <p>
* This method returns a new object based on this one with the specified period added.
* For example, on a {@code LocalDate}, this could be used to add a number of years, months or days.
* The returned object will have the same observable type as this object.
* <p>
* In some cases, changing a field is not fully defined. For example, if the target object is
* a date representing the 31st January, then adding one month would be unclear.
* In cases like this, the field is responsible for resolving the result. Typically it will choose
* the previous valid date, which would be the last valid day of February in this example.
*
* @implSpec
* Implementations must check and handle all units defined in {@link ChronoUnit}.
* If the unit is supported, then the addition must be performed.
* If unsupported, then an {@code UnsupportedTemporalTypeException} must be thrown.
* <p>
* If the unit is not a {@code ChronoUnit}, then the result of this method
* is obtained by invoking {@code TemporalUnit.addTo(Temporal, long)}
* passing {@code this} as the first argument.
* <p>
* Implementations must not alter this object.
* Instead, an adjusted copy of the original must be returned.
* This provides equivalent, safe behavior for immutable and mutable implementations.
*
* @param amountToAdd the amount of the specified unit to add, may be negative
* @param unit the unit of the period to add, not null
* @return an object of the same type with the specified period added, not null
* @throws DateTimeException if the unit cannot be added
* @throws UnsupportedTemporalTypeException if the unit is not supported
* @throws ArithmeticException if numeric overflow occurs
*/
Temporal plus(long amountToAdd, TemporalUnit unit);
//-----------------------------------------------------------------------
/**
* Returns an object of the same type as this object with an amount subtracted.
* <p>
* This adjusts this temporal, subtracting according to the rules of the specified amount.
* The amount is typically a {@link java.time.Period} but may be any other type implementing
* the {@link TemporalAmount} interface, such as {@link java.time.Duration}.
* <p>
* Some example code indicating how and why this method is used:
* <pre>
* date = date.minus(period); // subtract a Period instance
* date = date.minus(duration); // subtract a Duration instance
* date = date.minus(workingDays(6)); // example user-written workingDays method
* </pre>
* <p>
* Note that calling {@code plus} followed by {@code minus} is not guaranteed to
* return the same date-time.
*
* @implSpec
* <p>
* Implementations must not alter either this object or the specified temporal object.
* Instead, an adjusted copy of the original must be returned.
* This provides equivalent, safe behavior for immutable and mutable implementations.
* <p>
* The default implementation must behave equivalent to this code:
* <pre>
* return amount.subtractFrom(this);
* </pre>
*
* @param amount the amount to subtract, not null
* @return an object of the same type with the specified adjustment made, not null
* @throws DateTimeException if the subtraction cannot be made
* @throws ArithmeticException if numeric overflow occurs
*/
default Temporal minus(TemporalAmount amount) {
return amount.subtractFrom(this);
}
/**
* Returns an object of the same type as this object with the specified period subtracted.
* <p>
* This method returns a new object based on this one with the specified period subtracted.
* For example, on a {@code LocalDate}, this could be used to subtract a number of years, months or days.
* The returned object will have the same observable type as this object.
* <p>
* In some cases, changing a field is not fully defined. For example, if the target object is
* a date representing the 31st March, then subtracting one month would be unclear.
* In cases like this, the field is responsible for resolving the result. Typically it will choose
* the previous valid date, which would be the last valid day of February in this example.
*
* @implSpec
* Implementations must behave in a manor equivalent to the default method behavior.
* <p>
* Implementations must not alter this object.
* Instead, an adjusted copy of the original must be returned.
* This provides equivalent, safe behavior for immutable and mutable implementations.
* <p>
* The default implementation must behave equivalent to this code:
* <pre>
* return (amountToSubtract == Long.MIN_VALUE ?
* plus(Long.MAX_VALUE, unit).plus(1, unit) : plus(-amountToSubtract, unit));
* </pre>
*
* @param amountToSubtract the amount of the specified unit to subtract, may be negative
* @param unit the unit of the period to subtract, not null
* @return an object of the same type with the specified period subtracted, not null
* @throws DateTimeException if the unit cannot be subtracted
* @throws UnsupportedTemporalTypeException if the unit is not supported
* @throws ArithmeticException if numeric overflow occurs
*/
default Temporal minus(long amountToSubtract, TemporalUnit unit) {
return (amountToSubtract == Long.MIN_VALUE ? plus(Long.MAX_VALUE, unit).plus(1, unit) : plus(-amountToSubtract, unit));
}
//-----------------------------------------------------------------------
/**
* Calculates the amount of time until another temporal in terms of the specified unit.
* <p>
* This calculates the amount of time between two temporal objects
* in terms of a single {@code TemporalUnit}.
* The start and end points are {@code this} and the specified temporal.
* The end point is converted to be of the same type as the start point if different.
* The result will be negative if the end is before the start.
* For example, the period in hours between two temporal objects can be
* calculated using {@code startTime.until(endTime, HOURS)}.
* <p>
* The calculation returns a whole number, representing the number of
* complete units between the two temporals.
* For example, the period in hours between the times 11:30 and 13:29
* will only be one hour as it is one minute short of two hours.
* <p>
* There are two equivalent ways of using this method.
* The first is to invoke this method directly.
* The second is to use {@link TemporalUnit#between(Temporal, Temporal)}:
* <pre>
* // these two lines are equivalent
* temporal = start.until(end, unit);
* temporal = unit.between(start, end);
* </pre>
* The choice should be made based on which makes the code more readable.
* <p>
* For example, this method allows the number of days between two dates to
* be calculated:
* <pre>
* long daysBetween = start.until(end, DAYS);
* // or alternatively
* long daysBetween = DAYS.between(start, end);
* </pre>
*
* @implSpec
* Implementations must begin by checking to ensure that the input temporal
* object is of the same observable type as the implementation.
* They must then perform the calculation for all instances of {@link ChronoUnit}.
* An {@code UnsupportedTemporalTypeException} must be thrown for {@code ChronoUnit}
* instances that are unsupported.
* <p>
* If the unit is not a {@code ChronoUnit}, then the result of this method
* is obtained by invoking {@code TemporalUnit.between(Temporal, Temporal)}
* passing {@code this} as the first argument and the converted input temporal as
* the second argument.
* <p>
* In summary, implementations must behave in a manner equivalent to this pseudo-code:
* <pre>
* // convert the end temporal to the same type as this class
* if (unit instanceof ChronoUnit) {
* // if unit is supported, then calculate and return result
* // else throw UnsupportedTemporalTypeException for unsupported units
* }
* return unit.between(this, convertedEndTemporal);
* </pre>
* <p>
* Note that the unit's {@code between} method must only be invoked if the
* two temporal objects have exactly the same type evaluated by {@code getClass()}.
* <p>
* Implementations must ensure that no observable state is altered when this
* read-only method is invoked.
*
* @param endExclusive the end temporal, exclusive, converted to be of the
* same type as this object, not null
* @param unit the unit to measure the amount in, not null
* @return the amount of time between this temporal object and the specified one
* in terms of the unit; positive if the specified object is later than this one,
* negative if it is earlier than this one
* @throws DateTimeException if the amount cannot be calculated, or the end
* temporal cannot be converted to the same type as this temporal
* @throws UnsupportedTemporalTypeException if the unit is not supported
* @throws ArithmeticException if numeric overflow occurs
*/
long until(Temporal endExclusive, TemporalUnit unit);
}
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